P553: A PHASE 2, OPEN-LABEL, MULTIARM, MULTICENTER STUDY TO EVALUATE MAGROLIMAB COMBINED WITH ANTILEUKEMIA THERAPIES FOR FIRST-LINE, RELAPSED/REFRACTORY, OR MAINTENANCE TREATMENT OF ACUTE MYELOID LEUKEMIA
Authors: P. Vyas, N. G. Daver, M. P. Chao, G. Xing, C. Renard, G. Ramsingh, A. H. Wei, D. A. Sallman
Journal: HemaSphere (2022)

Background: Magrolimab (Hu5F9-G4) is an antibody blocking CD47, a macrophage immune checkpoint and “don’t eat me” signal on cancer cells. Magrolimab induces tumor phagocytosis and eliminates leukemia stem cells. Chemotherapy and hypomethylating agents synergize with magrolimab by inducing “eat me” signals on leukemic blasts, thereby enhancing phagocytosis. Magrolimab+azacitidine (AZA) has shown encouraging clinical efficacy with an objective response rate (ORR) of 63% and a complete remission (CR) or CR with incomplete hematologic recovery (CRi) rate of 54% in first-line acute myeloid leukemia (AML). Newly diagnosed AML patients (pts) who are ineligible for intensive chemotherapy (IC) are incurable despite the progress made with AZA+venetoclax (VEN; median overall survival [OS] 14-18 months), while AML pts with relapsed/refractory (R/R) disease after intensive regimens have a dismal prognosis. Furthermore, for pts in remission, maintenance therapy with oral AZA has improved OS and prevented relapse, although relapse rates remain high. Magrolimab combinations are being evaluated in each of these settings to improve the standard of care. Aims: To evaluate the safety, efficacy, and tolerability of magrolimab combined with antileukemia therapies in first-line pts ineligible for IC (cohort 1), R/R pts after IC (cohort 2), and pts in CR/CRi with presence of minimal residual disease (MRD) after IC (cohort 3). Methods: This is an open-label, multiarm, multicenter study that includes 3 safety run-ins with corresponding phase 2 cohorts. Pts in cohort 1 must be ≥75 years or 18-74 years with comorbidities that preclude IC. Pts in cohort 2 must have R/R AML after initial IC. Pts in cohort 3 must have achieved a CR/CRi with MRD positivity, as assessed by flow cytometry, after IC, and not be candidates for hematopoietic stem cell transplant. Each cohort will initially enroll 6 pts for 1 cycle (28 days) to assess dose-limiting toxicities and determine the recommended phase 2 dose (RP2D). Pts in cohort 1 will receive a combination of magrolimab, VEN, and AZA. Pts in cohort 2 will receive magrolimab in combination with mitoxantrone, etoposide, and cytarabine (MEC). Pts in cohort 3 will receive magrolimab with oral CC-486. All will receive magrolimab on the same schedule. In cycle 1, magrolimab will be administered intravenously (IV) as priming and ramp-up doses at 1 mg/kg on days 1 and 4, 15 mg/kg on day 8, 30 mg/kg on days 11, 15, and then weekly for 5 doses, followed by every other week beginning 1 week after the fifth weekly 30 mg/kg dose. For cohort 1, AZA (75 mg/m2) will be administered IV/subcutaneously on days 1-7 or 1-5, 8, and 9 of each cycle. VEN, MEC, and CC-486 will be administered according to labeled indications. After completion of the safety run-in, additional pts will be enrolled in cohort 1 (n=40), cohort 2 (n=30), and cohort 3 (n=40) for phase 2. In phase 2, pts in cohorts 1 and 3 will receive study treatment at RP2D until disease progression, unacceptable toxicity, or loss of clinical benefit. Pts in cohort 2 will receive magrolimab with MEC for up to 3 cycles followed by magrolimab alone for a total of 12 magrolimab cycles. In cohorts 1 and 2, the primary efficacy endpoint is the CR rate. Secondary endpoints of interest include OS, ORR, and MRD-negative CR/CRi rates. The primary efficacy endpoint in cohort 3 is the MRD-negative CR rate. Results: Trial in progress. Summary/Conclusion: Patient enrollment is ongoing. Clinical trial information: NCT04778410.